This invention relates to systems for cooling the atmosphere in a primary containment vessel of a nuclear power plant and for removing water-soluble gases and dust floating in the atmosphere of the primary containment vessel.
Drywell local cooling systems and containment spray systems are well known for cooling the atmosphere in the primary containment vessel of a nuclear power plant.
The drywell local cooling is a cooling system which cools the atmosphere in the drywell of a nuclear power plant. It system is generally used for providing and maintaining suitable temperature and humidity conditions within the primary containment vessel during normal operation of the nuclear reactor and the cooldown period for the atmosphere in the primary containment vessel and is arranged so as to circulate the atmosphere within the primary containment vessel through a heat exchanger by means of a blower and ducting system, cooling of the circulating atmosphere being effected by the heat exchanger.
Although the drywell local cooling system has enough cooling capacity to be applicable for cooling the atmosphere in the primary containment vessel during the normal operation and the cooldown of the nuclear reactor, it cannot sufficiently cool the atmosphere when radioactive vapor fills the vessel during an accident such as breaking of the piping system or a loss of coolant.
The containment spray system is particularly used for maintaining containment temperature and pressure within design limits in the event of loss of coolant and is arranged so as to spray cooling water in the primary containment vessel by means of a water spray device mounted on the upper portion of the vessel fed from a water supply source, to condense the radioactive vapor filling the vessel and to cool non-condensable gases.
However, when the containment spray system is operated at the event of the accident, the sprayed cooling water disperses through the atmosphere in the primary containment vessel and adheres to equipment such as machines, pipes or electric elements in the vessel and damaging their function or accuracy.